Author Topic: Starting work on speed tables. Fun with math.  (Read 409 times)

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daniel_leavitt2000

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Starting work on speed tables. Fun with math.
« on: March 23, 2018, 10:36:06 PM »
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I have an USB to NCE interface on the way, but until I have JMRI up and running, I will be working on programing decoders though the PowerCab.

I only have a simple oval of EZtrack for programing. It measures 39" X 54". Let's do a little math:

The circular section 39x3.14 = 122.46"
Add 40" to that total = 162.46 approx total track length.
162.46/12 = 13.5383 feet x 160 = 2166.33 scale feet
2166.33/5280 = .41 scale miles total for the loop.

If we wanted a top speed of 60 SMPH, that would by 60(seconds) x .41(scale miles) = 24.6 seconds to perform a full loop.

I want to program all my engines for a top speed of 70 SMPH. So the equation would be 6/7 = x/24.6, or (6/7) x 24.6 = 21.86 seconds to complete a loop of the test track.

More to come...
'In my great and unmatched wisdom'

djconway

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Re: Starting work on speed tables. Fun with math.
« Reply #1 on: March 23, 2018, 10:45:01 PM »
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I have almost the same setup except I have a tighter radius, such that my 70smph worked out to 15.29 seconds per loop.
The only caviot is just how close you can get it dialed in.  I have found that I can get to +/- 1..5 smph. Newer Atlas motors are better but still not 100%.

peteski

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Re: Starting work on speed tables. Fun with math.
« Reply #2 on: March 24, 2018, 12:27:20 AM »
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I doubt you guys will find perfection. It is also not required. Back in DC days we ran multiple unit lashups (on large NTRAK layouts) for hours using different brand locos (read: not closely speed matched) and they worked just fine.

Perfect speed matching is not required and with so many variables like glazing or carbon deposit on the commutator, lubricants with changing viscosity, the actual temperature of the motor and rest of the mechanism, varying component tolerances and assembly quality, you will never achieve perfect match at all times.  IMO, close-enough is good enough.
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jdcolombo

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Re: Starting work on speed tables. Fun with math.
« Reply #3 on: March 24, 2018, 09:49:44 AM »
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Or another way to do this is to buy a scale speedometer that fits over the track:

http://store.sbs4dcc.com/ModelRailroadTechnologiesAccutrackIITrainSpeedometer.aspx

I lot easier, IMHO, than trying to use a stopwatch to time your locos and probably more accurate in the end.  Actually, you can make your own speedo from parts, but it probably isn't worth the effort unless you wanted a permanent "speed trap" on your layout :)

As Peteski notes, you're not going to get speed matching perfect.  There are just too many variables (motor, gears, friction); but you CAN come awfully close, even with just using the "3-step" table of CV's 2, 6, and 5.

John C.

Urodoji

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Re: Starting work on speed tables. Fun with math.
« Reply #4 on: March 24, 2018, 10:21:14 AM »
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I match step 1 and step 28, and don’t bother with the rest. Once I have certain decoder/mechanism combination set up the way I want it, I create a master file and use it to quickly set up all locos with that combination.